This invention relates generally to prosthetic devices and systems, and more particularly to an implantable microstimulator which receives power and coded information via a radio frequency telemetry system.
The application of electrical stimulation to a living being is one of the primary techniques used in restoring function to the functionally-impaired. Additionally, such electrical stimulation has found application in the control of pain and may be useful in certain cases for the restoration of sight. There is presently in the art a great need for new and improved tools and techniques useful in the restoration of controllable function to patients having a wide variety of functional disorders. For example, neuromuscular electrical stimulation has been used to provide controllable hand movements in the upper extremity of spinal cord injury patients. Other important uses include the providing of respiration control to tetraplegic patients with respiratory paralysis; by stimulating the phrenic nerve, to void the bladder of paralyzed patients; and to treat urinary and anal incontinence.
It is, of course, of utmost importance that implantable tissue stimulation systems be designed to withstand long-term exposure to body fluids. Additionally, such electrical stimulators must be able to provide sufficient charge to effect the tissue stimulation, and to deliver the charge into the tissue reliably. It is further required that the stimulators be small, low in cost, reliable, and provide results which are reproducible.
Presently, most stimulators utilize discrete wiring to form stimulation electrodes, and therefore require relatively large (on the order of a few centimeters) packages to house the electronic circuitry and the power sources, which may include batteries and/or an antenna. There clearly is a need for improvements to electrical stimulator systems, in terms of both package dimensions and operating characteristics.
One of the most challenging areas in the field of implantable transducers has been the transfer of data and power into and out of the body of the living being. Although hard-wired systems have been generally used, they impose many problems on the overall structure in terms of:
(1) hermetic encapsulation at the entrance and exit points of the output leads;
(2) tethering effects due to the output leads;
(3) infection at the sight of the wires breaking the skin barrier; and
(4) low yield and labor intensive assembly and packaging.
In certain applications, the transmission of power and data using radio frequency telemetry has been employed with success. The known systems, however, employ implantable antennae that typically are required to be quite large in order to generate the requisite amount of power. Not only is there a need to reduce the size of the antenna, which may be on the order of several centimeters, but there is additionally the need to eliminate all external leads to the implant.
It is, therefore, an object of this invention to provide an implantable stimulator arrangement which is economical to manufacture and does not require external leads to obtain operating power and information.
It is another object of this invention to provide a microstimulator arrangement which can receive power and information from a radio frequency signal.
It is also an object of this invention to provide an electrical stimulator arrangement which can easily be implanted into a living being.
It is further object of this invention to provide an implantable stimulator system having an electrode which reliably can deliver high stimulation currents to a living being.
It is additionally an object of this invention to provide an implantable electrical stimulator system which avoids the problem of tethering due to the presence of output electrical leads.
It is yet a further object of this invention to provide a microstimulator arrangement which is hermetically encapsulated, and wherein the encapsulation is not compromised at the entrance and exit points of the output (electrode) leads.
It is also another object of this invention to provide an electrical stimulator assembly which avoids the problem of infection at the site where wires break through the skin barrier.
It is yet an additional object of this invention to provide an implantable microstimulator for neuromuscular stimulation which is easily and economically manufactured, achieving high yield and without labor-intensive assembly and/or packaging.